Automatic telephone-exchange system



March 16 1926.

M. B. KERR .w'rom'rm TELEPHONE EXCHANGE SYSTEM File April 2 10 Sheets-Sheet 1 March 16 1926.

M. B. KERR AUTOMATIC TELEPHONE EXCHANGE SYSTEM 1o Sheets-Sheet 2 the I Filed April 23 IIIIII hue/flak.- Mark 5? A? Much 16 1926. 1,577,033

M. a. KERR AUTOMATIC TELEPHONE EXCHANGE SYSTEM F 10 Sheets-Sheet s i l hvemor: J/d/k 15. Kay

March 16 1926. 1,577,033

M. B. KERR AUTOIIATIC TELEPHONE EXCHANGE SYSTEM Filed April 23, 1924 10 Sheets-Sheet 4 by iry March 16 1926. 1,577,033

M. B. KERR AUTUMATIC TELEPHONE EXCHANGE SYSTEM Filed April 23, 1924 10 Sheets-Sheet 5 March 16 1926. 1,577,033

M. B. KERR AUTOMATIC TELEPHONE EXCHANGE SYSTEM Filed A ril 23, 1924 10 Sheets-Sheet 6 hyemarx Mar/r5 Kerr March 16 1926.

M. B. KERR AUTOMATIC TELEPHONE EXCHANGE SYSTEM Filed April 25, 1924 10 Sheets-Sheet 7 hrs/man Mark 5 Kerr March 16 1926. 1,577,033

M. B. KERR AUTOMATIC TELEPHONE EXCHANGE SYSTEM Filed April 23, 1924 10 Sheets-Sheet 8 Mme/72W. Mark 5. Afr/r March 16 1926. 1,577,033

M. B. KERR AUTOMATIC TELEPHONE EXCHANGE SYSTEM Filed April 25. 1924 10 Sheet s-Sheet e by My 4 7 Patented Mar. 16, 1926.

UNITED STATES PATENT OFFICE.

MARK IB- KERR, O! ROSEBANK, NEW YORK, ASSIGNOR TO WESTERN ELECTRIC COM- PATTY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

AUTOMATIC TELEPHONE-EXCHANGE SYSTEM.

Application filed April 28, 1824. Serial No. 708,358.

To all whom it may concern:

Be it known that I, MARK B. KERR, a citizen of the United States of America, residing at Rosebank, Staten Island, in the county of Richmond and State of New York, have invented certain new and useful Improvements in Automatic Telephone-Exchange Systems, of which the following is a full, clear, concise. and exact description.

This invention relates to automatic telephone exchange systems and more particularly to systems in which subscribers lines terminate in different exchanges and wherein trunks are provided for completing connections between the lines in the several exchanges.

In a multi-oflice telephone system there are provided groups of trunks for interconnecting subscribers lines in any two main offices. However, in such systems where a comparatively large number of offices are situated within the same area and the traffic between offices is heavy, considerations of economy necessitate the routing of a certain amount of this traflic through a central or tandem office which serves as a common intermediate distributing point for traffic between the several main offices.

It is an object of this invention to render more efficient the comparatively small number of direct office trunks by automatically rerouting the abnormal or overflow trafiic to a tandem point Where it is directively routed to the desired point.

A feature of the invention relates to a common controlling mechanism which functions in accordance with the recorded designations of wanted lines, the controlling mechanism being so arranged that its normal function corresponds to such a recorded designation with means for automatically revising the controlling function of such a mechanism when certain traffic conditions occur.

Another feature of the invention relates to a common controlling mechanism which receives. in a translated form, called line designations, and subsequently controls the operation of selective switches in accord ance with the translated record together with means for allowing the first translated record to be nullified and a new translation to be effective when in its controlling operations the common mechanism encounters abnormal trafiic conditions.

A further feature of the invention relates to a system in which groups of direct trunks are provided between calling and called offices and other groups of trunks are provided for giving access to a called office by means of an intermediate or tandem office, the arrangement of the circuits being such that when all the first group of trunks are busy, an idle one of the second group of trunks is selected, which trunk is located in a different switch from that in which the first group of trunks is located.

Another feature of the invention relates to telephone systems wherein markers are used, the said markers being adapted to control the operation of selective switches to extend a calling line directly to acalled ofiice or by means of an intermediate or tandem office, the arrangement of the markers being such that when all direct paths to a called office are busy, the marker functions auto matically to reroute the call through a tandem oflice.

A still further feature of the invention relates to the means for indicating to a controlling sender whether the calling line is to be extended to a distant office directly or by means of an intermediate office, these class-of-service indications being normally dependent upon the called line designation together with means for automatically changing the original class-of-service indication in the sender when traffic conditions necessitate the extension of the calling line through a tandem ofiice.

Another feature of the invention pertains to a telephone system wherein switches of the coordinate type are employed and wherein a marker or controlling mechanism is adapted to test the condition of the link circuits in a plurality of switches and the condition of the trunks outgoin from these switches prior to the operation of either thereof.

Other features and advantages of the invention will be better understood after reference to the following description and the ap nded claims.

he accompanying drawings when arranged in the or er shown m Fig. 11 illustrate in sufiicient detail a preferred form of carrying out the invention.

Fig. 1 illustrates. to the left and above the broken line, one of a number of coordinate line switches in which the subscribers lines appear. Terminating in certain contacts of this switch are also shown a number of outgoing district trunks. To the right and above the broken line is shown certalncontrolling equipment associated with one of the district trunks. Below the broken line is shown a sender selector switch also of the coordinate type.

Fig. 2 illustrates a coordinate distr1ct selector switch. This figure also shows within the dotted rectangle, a diagrammatic representation of a tandem ofiice with incoming and outgoing trunks.

Fig. 3 shows one of a number of coordinate office selector switches in which trunks, outgoing from the district selector switches, terminate. In this figure is also shown schematically a distant called ofiice.

Fig. 4 shows in diagrammat c form, a subscribers register and controlling sender, and a device for connecting said sender to a common controlling mechanism or marker. This figure aiso illustrates schematically the mechanism for transmitting characteristic im ulses over the outgoing trunks to cont oi automatic switches at distant oflices.

Fig. 5 to the left of the broken line 1llus trates one of a number of district frame con nectors for connecting the test and operating conductors of the district switches to the testing mechanism in the marker. To the right of the broken line is shown a district trunk connector for allowing the marker to test the condition of the trunks outgoing from the district selector switches.

Fig. 6 shows an office frame connector and an oiiice trunk connector, which in connection with office selector switches, function similarly to theconnectors shown in Fig.5

Figs. 7, 8 and 9, when taken together, disclose one of a number of markers or common controlling mechanisms which are as sociable with any calling line.

Fig. 10 is a schematic layout of a system embodying the features of the invention and to which reference will be made in the following general description.

General descm'ptz on.

The line switch 100, sender selector switch 150, district selector switch 200 and ofiice selector switch 300 are all of the coordinate type, such as disclosed in the U. S. patent to C. L. Goodrum and J. N. Reynolds, No. 1,515,735, issued Nov. 18, 1924,

and also in the patent to S. B. \Villiains J12, No. 1,517,331, issued December 2, 1924. These switches consist, in the main, of a plurality of operating bill?) and a pluraiity of horizontal conducting links, the selective operation being determined by the conjoint operation of a particular vertical bar and an operating member associated with a particular horizontal link.

Referring to Fig. 10, it will be seen that the subscribers lines such as 1001 have an appearance in the vertical rows of contacts of a line switch such as 100; The selective operation of a line switch in response to the initiation of a call on a subscribers line automatically connects the said line to an idie one of the district trunks 1002 which terminate in contacts of district selector switches, as 1015. At the same time that the calling line is extended to the district selector switch, the operation of a sender selector switch as 1005 is initiated. The switch 1005 in its selective operation associates an idle one of the register senders 1006 with the calling line. The sender receives and records the designation of the wanted line as dialed by the calling subscriber. When the code or oiiice portion has been thus recorded, connecting device 1009 is o erated to connect the register sender wit an idle marker or controlling mechanism 1010. The latter operation takes place in such a manner as to preclude more than one sender being connected to the same marker. Immediately that the connector device 1009 is operated, the oflice portion of the recorded designation is transferred from the sender 1006 to the marker.

Each of the district frame connectors, as 1011, is related to a particular vertical row of contacts in the sender selector switch 1005. Therefore, the operation of a vertical magnet in the switch 1005 at the same time serves to identify the particular district frame in which the extended calling line appears, and also causes the operation of the corresponding district frame connector. With frame connector 1011 operated, the group of testing and operating conductors 1032 and 1033 are extended to the testing equipment located in the marker 1010. for the purpose of determining and selecting an idle horizontal link.

The oilice designation as recorded in the marker is translated therein in such a manner as to cause the operation of an office trunk group relay which identifies the desired oflice trunk group. The operation of this office trunk group relay in turn controls the operation of a corresponding district trunk group relay. Thus the oflice code portion of a called line designation serves to locate the selected grou of trunks in the district and oflice switc es. Vith the proper district trunk group relay operated,

a circuit is closed to operate the proper one of the district trunk connectors 1012. The frame and trunk connectors 1011 and 1012 now cooperate to actuate a particular vertical magnet in the district selector switch 1015 which magnet is associated with the desired group of trunks outgoing from switch 1015.

At this point, it should be observed that the trunks leading from the district selector switch are arranged in a number of groups,

such as group 1010 and group 1017. The group of trunks 1010. it will be further observed, lead to an oflice selector switch 1060 whereas the group of trunks 1017 lead to the tandem office 1050 which is shown schematically.

It is clear, therefore, that the translation in the marker of the oflice code determines the particular group of trunks, whether tandem or direct, over which the calling line will be extended. Assume for a moment that the call is of such a nature as to necessitate the use of trunk group 1010. The operation of the district trunk group relay as a result of translation in the marker determines the operation of the proper one of the vertical magnets associated with this desired group of trunks leading from the district selector switch. At this time also the sleeve conductors of this group of trunks are connected by means of the trunk connector 1012 to the testing equipment in the marker 1010. Also the operation of the office trunk group relay causes the operation of the proper otiice frame and trunk connectors as 1013 and 1014. The frame connector 1013 functions to connect the office testing equipment in the marker to the horizontal links in the switch 1060 and the trunk connector 1014 functions to connect the test conductors of the selected group of oifice trunks to the testing equipment.

The testing mechanism is of such a nature that a simultaneous test is made both of the links and the outgoing trunks, in both the district and oflice switches, and neither the switch 1015 nor switch 1060 is operated until idle paths through and from said switches have been found. Should, however, there be no available cross-points in the district switch, a signal is transmitted to the sender 1006 and a characteristic busy tone transmitted back to the calling subscriber. Should, however. an available cross-point be located in the district switch, as well as an idle trunk outgoing from the office switch, circuits are closed to operate the proper horizontal connecting magnets in both of these switches, thus extending the calling line through contacts of the line switch 1003, district switch 1015, otiice switch 1060 to a trunk in group 1018 which leads to the desired oflice.

Returning to the point where the test conductors of the trunks outgoing from the oflice switch were connected by means of trunk connector 1014 to the marker testing e uipment, should all the trunks in the se ected group 1018 be busy, notification will be sent to the marker which will cauw the release of the operated translator mechanism, testing mechanism and the district trunk group relay. At the same time a transfer relay will be operated in the marker which will automaticall function to operate another district trun group relay which is associated with a group of trunks as 1017 leading to a tandem oflice. The operation of this second trunk group relay will cause the operation of the corresponding verticalmagnet of the district selector switch. \Vhen an idle one of the trunks leading to the tandem office is located, the calling line is extended through contacts of the district switch to a tandem trunk in group 1017, and thence to a tandem office shown schematicaly at 1050. The impulsing mechanism 1008 is now connected through contacts of switch 1005 to the trunk 1002 for the purpose of controlling selection through the switches in the tandem office 1050. For the manner in which these impulses are transmitted to perform the above operation, reference may be had to the patent to S. B. illiams and E. S. Gibson, No. 1,543,967, issued June 30, 1925. The numerical portion of the designation as recorded in sender 1006 is now transferred in the manner described in the above mentioned application to the register and controlling sender 1020 located in the tandem ofiice, which functions to selectively operate the incoming switch 1024 to select an idle trunk, such as 1030 leading to the desired oiiice 1080. From the above description, it will be seen that a test is made of the trunks outgoing from the district and otiicc selector switches, the operation of these two switches being contingent upon the finding of an idle trunk giving access to the called oiiice. the event that such a trunk is not found the recording mechanism in the marker is released and a new record automatically set up so as to give the calling line access to a tandem trunk which leads directly from con- 1 tacts of the district selector switch.

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For the purpose of better illustrating the use of the invention. let it be assumed that the subscriber at station 101 desires to com niunicate with another subscriber whose line terminates in a dili'erent ofiice. such as shown diagrammatically at 350 to which a number of direct trunks 300, 301. etc. lead. The removal of the receiver by the calling subscriber causes the line switch 100 to operate to extend the line 102 to an idle trunk such as 10?. 'hcn the calling line loo has been so extended the sender selector switch 150 is also caused to operate to associate an idle sender 400 with the calling line. \Vhen a sender has been thus associated, relays 104 and 401 operate to ground at the armature of sender selector control relay 105. Relay 105 subscqiwntly releases but relays 104 and 401 remain locked to the sender control ground 402. Relay 104 in operating transfers the tip anl ring conductors of the calling line from the outgoing trunk to the windings of impulse relay 403 and retardation coil 404. The circuit is now in readiness to receive impulses transmitted by the calling subscribers dial. Relay 403 follows the impulses and causes them to be recorded on the registers 440. \Vhen the code or otlice portion of the called line designation has been transmitted and recorded on the registers, the connecting device 450 is operated to connect the sender with an idle outgoing marker, such as shown in Figs. 7, 8 and 9. whereupon the record of the office code is transferred from the sender registers 440 to the marker registers 700.

For a detailed description of the manner in which the above operations take place, reference may be had to the application of \V. Y. Carpenter, Serial No. 7 03,362, filed April 1, 1924.

\Yhen the sender connector 450 operates, the marker start relay 405 is actuated and connects battery through its armature and contact. contacts of connector 450. conductor +30, to battery through the winding of marker ground control relay 701. Then the connector 450 operated. circuits were also closed as described in the above mentioned application. Serial No. 703,302, filed April 1. 1924. to operate all the recording relays 700. (ertain of these recording relays operate over circuits traceable through front contacts to the operated register relays in the register set 140, while the remainder of the relays 7 00 operate in circuits traceable through normal contacts of the unoperatcd sender reg ster relays. \Vhen all the relays 700 have been operated. a circuit is complcted from ground at the upper armature and contact of relay 710, upper armature and contact of the remaining recording relays in series to battery through the winding of relay 702. Relay 702 operates and completes an obvious circuit for relay 703. .Vheu relay 703 operates it closes a circuit for relay 7 04 traceable from battery, through the winding of the said relay, left armature and front contact of relay 703, leftv armature and back Contact of relay 705, right armature and back contact of relay 706 to ground at the right armature of relay 701. The operation of relay 7 03 also causes the release of those recording relays 700 which were operated through normal contacts of sender register relays so that only those recording relays remain operated which correspond to the operated sender register relays. The manner in which the former relays release is described in detail in the application, Serial No. 7 03,362, filed April 1, 1924, hereinbefore referred to. It will be apparent from an inspection of the drawing that the registers 720, 721 and 722 correspond respectively to the first, second and third digits of the ofiice code. Assume for the purpose of this description that the record on the sender registers 440 has caused the marker recording relays 711, 712 and 723 to remain operated. The translator 750 is now operated in such a manner as to cause the actuation of a particular one of the office trunk group relays as 901, 902, etc. The particular combination of operated and unoperated relays in registers 720 will determine the operation of the proper one of the multi-contact relays 707, 708, etc. In a similar way. the register 721 determines which one of the relays 709. 714, etc., will be operated. Each of the ten relays 709, 71-1, etc, carries ten contact sets, but for the purpose of economy in the drawing a fewer number of these relays and a fewer number of their contact sets are shown. Finally, the register 722 determines which one of the operated contact sets will be effective in Tpcrating the proper office trunk group re- 'hen the first digit of the oflice designation has been-transferred to register 720, a circuit is closed from the grounded conductor 740, armature and front contact of relay 704, lower inner armature and contact of relay 715, lower inner armature and front contact of relay 711 to battery through the winding of relay 707. The transfer of the record to register 721 causes the operation of relay 714 in a circuit which may be traced from battery through the winding of the said relay, lower inner armature and back contact of relay 716, lower inner armature and front contact of relay 712, lower inner armatures and back contacts of relays 717 and 718 to ground as above traced. The record on register 722 extends the same ground through the lower inner armature and contact of relay 724. lower inner annature and front contact of relay 7 23, upper outer armature and (ontact of relay 714, contact of relay 707, and thence by means of connecting block 760 and conductor 857 to battery through the winding of office trunk group relay 901. Relay 901 operates and closes a circuit from ground through its right inner armature and contact, conductor 960, contacts of sender connector 450, to battery through the winding of the class relay 406. Relay 406 operates and serves as an indication to the sender that this particular call is to be extended directly to a distant oflice.

Ew-r. of the relays 410 and 411 relates to a particular district frame such as 200. Since the extended calling line appears in district switch 200, it will be necessary to operate relay 411 associated therewith. Furthermore, each of the vertical rows of contacts in the sender selector switch 150'is also re-' lated to a particular group of trunks terminating in the several district selector switches. Since vertical magnet 160 was operated as a result of the seizure of trunk 103,

a circuit is closed from ground atthe lower inner armature and contact of magnet 160, condu tor 460, winding of rela 408 to battery. Relay 408 closes a circui through the contacts of connector 450, to battery through the winding of relay 411 which operates. Since the district selector frame is now identified a circuit is completed to opprate frame connector 500 So as to council; t e group of conductors 250 to the district test e uipment 800 located in the marker. Accor ingly, a circuit is completed from ground at the left armature and back contact of relay 501, left winding of relay 502, conductor 451, arms ture and contact of relay 411, left armature and contact of relay 725, left armature and contact of relay 701, conductor 430, contacts of connector 450, to battery at the armature and contact of relay 405. Relay 502 locks through its right hand windin in series with the winding of relay 501, w ich operates, thus preventing more than one district frame bein simultaneously associated with this mar er. Relay 501 also extends ground through its left armature and front contact, left inner armature and front contact of relay 502 to battery through the winding of relay 509. Relays 502 and 501 close an 0bvious circuit for the multi-contact relay 516 which is individual to the. particular marker shown.

A circuit to operate district trunk vertical ma et 201, 1s now closed from-battery throug the winding of said ma net, conductor 256, lower armature and rent contact of relay 104, conductor 151, contacts of sender selector 150, conductor 453, contacts of connector 450, conductor 452, left armature and contact of relay 801, conductor 850, to ground through the left inner armature and contact of relay502,- Magnet 201 prepares the vertical row of contacts 210 and extends the above traced ground through its lower armature and front contact, 0011- ductor 251, to batterythro'ugh the winding of multi-contact relay 516. An obvious circuit is now completed for operating relay 504 which is individual to the group of trunks which includes trunk 103 and which terminate in district switch 200. The operation of relay 504 completes acircuit for the particular one of the district trunk group relays 506, 507. etc.. whose circuit has been partially completed by the operation of the for the multi-contact rela nector 550 operated,

ofiice trunk relay 901. The circuit for this purpose may be traced from batte at thearmature and contact of relay 50 wind: ing of relay 508, conductor 551 to ground at the right outer armature and contact of relay 901. from ground through its right outer arma- Relay 508 completes a circuit ture and contact, conductor 556 to battery through the winding of rela 802 .whic o crates for purposes hereina er descr'bed. 1th relay 508 operated, a circuit is a so completed for actuating the district tru connector 550 in such a we as to connect the test conductors of the se ected group of district trunks tothe marker testing mechanism. Accordingly, relay 511 operates in a clrcuit traceable from ground at the armature and back contact of relay 512, right winding of rela 511, next to innermost right contact an armature of relay 508 to b'atterfieat the armature and contact of rela 509. ing in series with relay 512 which operates. An obvious operating circuit is now closed 513 which is individual to the marker 3 own. Another circuit is com leted for multi-contact relay 510 which is individual to the group of selected district trunks. The circuit for this purpose may be traced from battery through the winding of rela 510, innermost armature and contact 0 relay 508, right inner armature and contact of relay 511 to ground at'the armature and contact of relay 512. A circuit is now completed for the vertical magnet 214 associated with this group of trunks. This circuit may be traced from battery through the winding ofma et 214, conductor 254, left armature an contact of relay 508, conductor 557, ri ht armature and contact of relay 805, con uctor' 854, to ground through the contacts of relays 513 and 510. Relay 801 also o states in a cir cuit traceable from battery t rou'ghits wind ing, conductor 855, contacts of frame oonnector 500, conductor 257 to ou-nd at the lower armature and contact 0 magnet 214. The operation of relay 801 opens the original operating circuit of vertical magnet 201 but this magnet remains locked to grounded conductor 251.

With frame connector 500 and trunk conthe test conductor'of the horizontal links in switch 200 as well as the test conductors of the group of trunks which includes trunks 252 and 253 are new extended to the district testing mechanism 800.

It will be observed that each of the, test relays 810. 811, 812, etc., has its left winding connected through contacts of frame. connector 500 to the several horizontal links in the switch 200. Similarly, the right hand windings of these test relays are connected by means of trunk connector 550 to the test lay 511 looks through its left win is made by means of the connectin conductors of the selected grou of district trunks. Should either a t or a link be busy, the test relay connected thereto will be operated, thus providing a test of all available cross oints in switch 200. It will be further 0 served that provision blocks 552, 553, etc., for rendering effective certain portions of the testing relays 111 accordance with the maximumnumber of the trunks in the group to be tested. For example, assume that trunk 253 is the first trunk in this group then by means of the block 553 the test conductor is connected to the right winding of relay 811. Assume trunk 252 to be the last trunk in this group then its test conductor is connected to the winding of relay 810. In a similar manner, other trunks in this group will be connected to corresponding relays. Should all available cross points in switch 200 be busy, then a circuit is closed from battery through the windin of relay 814, conductor 851, contacts o relays 513 and 510, loop 555, returning through contacts of relays 510 and 513 conductor 558, right outer armature and front contact of relay 810, right outer armature and front contact of relay 811, conductor 856, contacts of rela s 513 and 510, loop 559 returning througi contactsof relays 510 and 513, conductor 561, n ht outer armature and contact of relay 801, eft outer armature and contact of rela 805, to the grounded conductor 753. Re ay 814 operates and connects ground through its right 'outer armature and contact to conductor 816 which ma serve as an indication to the sender that al paths through this district switch are busy, and in the manner described in the patent to S. B. Williams, Jr.,'No. 1,517,331, issued December 2, 192 1, a tone is sent back to the calling subscriber as a busy indication.

Assuming, however, that trunk 252 and link 211 are both idle, a circuitis completed to operate relay 817 associated with this idle cross point. This circuit may be traced from'battery through the winding of relay 817, right outer armature and back contact of relay 810, right outer armature and front contact of relay 811, conductor 856, contacts of relays 513 and 510, loop 559, returning through contacts of relays 510 and 513, conductor 561, to ound as above traced. With relay 817 operated a circuit is prepared from battery, through the right winding of magnet 215, conductor 258, contacts of connector 500, conductor 562, left outer armature and contact of relay 817 to the right inner armature of.relay 802. However, relay 802 being operated, prevents the operation of magnet 215 until a test has been made of the links and trunks in the oflice switch 300.

When trunk connector 550 operated, a circuit was completed from battery through connects battery through its the characteristic resistance 310, sleeve con ductor of trunk 252, conductor 255, contacts of relays 510 and 513, conductor 852, right armature and front contact of relay 817, left armature and front contact of relay 802, conductor 853, lower armature and back contact of relay 903, winding of marginal relay 904, to ground through the winding of relay 905. Assuming that resistance 310 is of such a value as to permit the operation of relays 904 and 905, it will be seen then that the combination of marginal relay 904 and resistance 310 provides a means for identifying the oilice frame to which the calling. line is to be extended. It will be remembered that the selected group of trunks which includes trunk 252 was identified by the operation of district group relay 508. In a similar way the location of this group of trunks is identified by the operation of relay 601. Relay 601 operated at substantially the same time that relay 508 operated over an obvious circuit. Relay 601 now closes a circuit to operate relay 602 which is individual to the switch 300. The circuit for this purpose may be traced from battery through the winding of relay 602, left inner armature and contact of'relay 601, conductor 657, left armature and front contact of relay 904 to ground at the armature and contact of relay 905. Relay 602 locks through its winding and locking contact, conductor 651, left armature and back contact of relay 705, right armature and back contact of-relay 706, to ground at the armature and contact of relay 701. Relay 602 left inner armature and contact, left winding of relay 603 to ground at the armature and contact of relay 604. Relay 603 locks in series with relay 604 which operates. Relay 603 closes a circuit for the multi-contact relay 605traceable from battery through the winding of the latter relay, left inner armature and contact of relay 603, conductor 656, armature and back contact of relay 906 to the grounded conductor 753. Relay 603 in con- 3unction with oflice frame relay 602 also completes a circuit for multi-contact relay 606. This circuit may be traced from battery through the winding of relay 606, left outer armature and contact of relay 602, leftjnner armature and contact of relay 603 to ground over conductor 656, as above traced. A circuit is now completed from ground at the armature and back contact of relay 608, right winding of relay 609, conductor 653, left armature and contact of relay 901, conductor 963, right outer armature and contact of relay 603 to battery at the left inner armature of relay 602. Relay 609 operates in this last traced circuit and looks through its left winding in series with the winding of relay 608, which operates. An obvious circuit is now completed for the nmlti-contact relay 607, at the same time a circuit is completed for operating the multicontact relay 610 which is associated with the group of trunks which includes trunks 360, 361, etc. The circuit-for operating relay 610 is traced from battery through its winding, conductor 658, left armature and contact. of relay 901, conductor 669, right iuncr armature and contact of relay 609 to ground at the armature and front contact of relay 608. i

A circuit is now completed for vertical magnet 311 traceable from battery through the winding of said magnet, conductor 351, contacts of connector 650, conductor 659, left outer armature and contactof relay 901, conductor 961, to ground through the contacts of relays 607 and 610. Magnet 311 prepares the vertical row of contacts 312 and extends ground through the lower armature and contact, conductor 31 1 cont-actsof connector 650, conductor 962, to battery through the, winding of relay 903. Relay 903 operates and opens the circuits of relays 904 and 905.

\Vith connectors 650 and 655 operated, the test conductors of the links and trunks outgoing from switch 300 are connected to the ottice test mechanism 900. Assuming that trunk 360 is the first of its group and trunk 361 the last, then from an inspection of the drawing it will be seen that the test conductor of trunk 360 is connected to the. right hand winding of relay 907 and the test conductor of trunk 361 is connected to the right hand winding of relay 909. In a similar manner, test conductors of other trunks in the group are connected to the right hand windings of corresponding test relays. Assuming for the present that trunk 361 and the link 320 are both idle'then relay 909 associated therewith is normal, and a circuit is completed from battery through the winding of relay 910, ri ht outer armature and back contacts of relay 909, right outer armatures and front contacts of preceding test relays conductor 964, contacts of relays 607 an 610, loop 611, returning through contacts of relays 610 and 607. conductor 662, upper outer armature and contact of relay 903, armature and back contact of relay 906 to the grounded conductor 753.

An idle trunk having been found outgo ing from switch 300, a circuit is now closed for operating horizontal magnet 215 in the district switch 200. This circuit ,ma be traced from battery, through the right and winding of magnet 215, conductor 258, contacts of relays 503 and 516, conductor 562 left outer armature and front contact oi relay 817, ri ht inner armature and front contact of re ay 802, conductor 858, right inner armature and contact of relay 910 to the grounded conductor 753. Magnet 215 operates and completes the connection of lay 903. Relay trunk 103 with trunk 252 by means of link 211. A circuit isnow completed for operatiug'vertical magiit 315 traceable from battery through the winding of said magnet, left armature and back contact of relay 317 tip conductor of trunk 252, contacts 01. switch 200, tip conductor of trunk 103 con ductor 151, contacts of switch 150, conductor 453, contacts of connector 450, conductor 452, left outer armature and contact of relay 603 to ground at the armature and contact of relay 604. This same ground is extended through the lower inner armature and con-' tact of magnet 315, conductor 318, contacts of connector 650, conductor 663, upper inouter armature and contact of relay 910, conductor 965, contacts of connector 650,

conductor 35 1 to battery, through the right hand winding of magnet 316. A circuit is now closed from battery, through both windings of magnet 316 in series, contact of switch 300,- sleeve conductor of the trunk, left winding of relay 317 to the sleeve of trunk 252 which is grounded in the manner described in the above mentioned a plication of \V. WV. Carpenter I 703,3 2, filed April 1, 1924. Relay 317 does not gperate at this time, however, sinceits operating winding is shunted by the ground a we traced for operating magnet 316. The operation of magnet 316 completes the connection through the switch 300.

When horizontal magnet-215 operated, a.

753 through its armature and front contact,

conductor 815, armature and back contact of relay 719, contacts of connector 450 to battery, through the winding of sender release relay 114. In the manner described in the' above mentioned application of W. W. Carpenter, Serial No. 703,362, filed April 1,1921, relay 414 causes the release of sender connector 450 and the release ofthe operated translator relays 700. The release of the translator relays in turn causes the release of oflice trunk group rela 901 and district trunk relay 508. It wil be remembered that when trunk vertical magnet 311 operated, it closed a circuit for actuating re- 903 in turn opened the energizing circuit of slow release relay 904 which began to release. The release period of relay 904 is of sufiicient length to per! mit the testing and operation of the district and office horizontal magnets. When district trunk group relay 508 released, it in her armature and contact of relay 003, left Serial 0.

turn released relay 802. The release of re lay 802 now completes a circuit from battery through the windin of relay 808, left inner armature and hue contact of relay 802, right armature and front contact of relay 8'17, conductor 852, contacts of connector 550 to the rounded sleeve conductor of trunk 252. W en trunk group relay 508 released, it also caused the; discharge of trunk connector 550; and when relay 602 releases as a result of the release of relay 904 the oflice frame and trunk connectors 650 and 655 are also released.

As soon as horizontal ma net 215 operated, the function of the mar er in controlling selection through the oflice and district frames was finished and a circuit completed from battery through the windin of relay 725, lower inner armature and iont contact of relay 903, conductor 853, left inner armature and front contact, of relay 802, rght armature and front contact of relay 8-17, conductor 852 and thence to the grounded sleeve conductor of trunk 252. Relay 725 operates and opens the locking circuit for ground control relay 701 which releases, in turn causing release of the district frame connector 500. The release of the several frame and trunk connectors in turn causes the release of the operated vertical magnets connection through the office and district switches being maintained by the continued energization of horizontal magnets 316 and 215 respectively. When office frame connector 650 releases, the shunt is removed from the winding of relay 317 which operates ings of magnet 316. The operation of re lay 317 completes the circuit of the tip conductor of trunk 252. The marker is now discharged and made accessible to other calling lines.

The local district trunk 103 is now connected to the outgoing trunk 361 which leads to the desired cities, and when the complete numerical designation has been, recorded on the registers 440, the sender having fpreviously been notified of the character 0 this particular call, the impulsing mechanism 420 functions to send characteristic impulses over the tip and ring conductors of the outgoing trunk to control the operation of the selective switches at the distant oflice. For the manner in which the sender adjusts itself upon the receipt of the class designation and for the manner in which the said impulses are transmitted, reference may be had to the patent to S. ll. Williams and E. S. Gibson, Patent No. 1,543.967, issued June 30, 1925. When the sender has completed the above functions, switch 150 is released, causing in turn the release of the sender. The release of the sender also causes the release of relay 104 and the calling line 102 is new extended a tandem oiiice such as 260,

tandem ofiice 260.

in series with both wind-' Normal tandem operation.

Should the line of the subscriber with whom the subscriber atstation 101 desire: to converse be located in a distant ofiice to which no direct trunks lead from the cal]- ing subscribers ofiice, then it becomesneoessary to extend the calling line by means of a trunk, such as 261, 262, etc., leading to and thence by means of a trunk 267 to the desired called office.

The operation in such a case is similar to that already described as far as the point where an oflice trunk group relay isto be operated. From an inspectionv of Fig. 2, it will be seen that a certain grou of trunks including-trunks 261 262, etc., liead to the O onsequently, it-will be necessary, in order to gain access to ,one of these trunks to operate vertical magnet 216.

Assuming that as a result of the calling subscribers manipulation of his dial, the transfer of therecord from the sender registers 440 to the marker register 700 results in the operation of relays 710, 716, and 723. Accordingl in the manner already described, mu ti-contact relay 727 operates as well as relay 726. With this combination of translator relays operated, marker ground is extended through the contact of relay'704, lower inner armature and contactrof relay 724, lower inner armature and front contact of relay 723, armature and contact of relay 726, contact of relay 727, cross connecting block 760, conductor 755 to battery, throu h the winding of tandem trunk group re ay 806. The operation of relay 806 connects ground through its inner armature and contact, conductor 455, contacts of connector 450 to battery throu h the winding of tandem class relay 415. The operation of relay 415 serves as a class of call indication to the sender. In addition, relay 806 extends ground through its outer armature to conductor 859, winding of group relay 507, to battery at the armature and contact of relay 504. Belay 507 identifies the roup of trunks outgoing from district switc 200 to the tandem office 260. Belay 507 also causes the actuation of connector 550 by operating relays 513 and 515. The operation of the district frame and trunk connectors and the testing of the several trunks 261, 262, etc, is accomplished in the manner already described. In this case, however, there being no oliice selection required, neither the office frame nor the ethos trunk connector is operated. When an idle one of these tandem trunks is located, the corresponding horizontal magnet is actuated and the local district trunk 103 s extended through contacts of switch 200 to the tandcm'ollicc. Assuming that the extension of theca-lling line as been completed through link 266, a circuit is there upon completed from battery, through the winding of relay 808, left inner armature and back contaict of relay 802, right armature and front contact of relay 809, conductor 861, contacts of rela s 513 and 515 to the grounded sleeve con actor of trunk 263; Relay 808 looks to the groundsd coniuctor 753. The cpmrationof relay 808 i150 closes a circuit rom the grounded conductor 753, right armature and contact of relay 808 to battery, through the winding of relay 805. Relay 805 at its left outer armature and back contact breaks the hold ing circuit for the qigrated test relays 800 which now release. clay 805 at its right armature and back contact also opens the euer in circuit of vertical magnet 216 whie re eases. When relay 808 operated,

it also extended the grounded conductor 753 through its left outer armature and front contact, left outer armature and back con-. (act of relay 802, conductor 815, armature and back contact of relay 719, contacts of connector 450 to butter through the winding of sender release re ay 414. In the manner before mentioned, relay 414 causes the release of sender connector 450 and the operated relays in the marker. The release of the marker relays causes the discharge of connectors 500 and 550 which in turn causes the release of vertical magnet 201 as already described.

The sender having previously received a class of service indication now functions to retransmit sets of impulses to control the operation of the incoming selector switch at the tandem ollice. The operation of this latter switch causes the selection of an idle trunk, such as 267 which gives access to the called ofiice 850. Inasmuch as the manner of controlling the switches at the tandem office to select such a trunk is not a feature of this invention, a detailed description thereof is not deemed necessary.

Automatic rerouting through tandem ofice.

It will be remembered in connection with the first detailed description that a test was made both of the trunks outgoing from the switch 200 as well the trunks outgoing from switch 300 prior to the operation of either of the switches. Returning, then, to the int where the sleeve conductors of the inks and trunks in switch 300 were connected to the test relays 900, let it be assumed that all cross points giving access to the group of trunks including trunks 360, 361, etc., are busy. Accordin ly, the test relays 907, 908, etc, are 0 crate and a circuit is closed from battery t rough the winding of tandem transfer relay 911, left inner armature and front contact of relay 001, conductor 968,

contacts of rela 607 and'610, loop 064, rc-

turning throng ncontacts of relays 010 and 607 conductorftitlli, right outer armaturcs and front contacts of all the operated test relays, conductor 064, contacts of relays 607 and 610, loop 611, returning through contacts of relays 610 and 607, conductor 062, upper outer armature and contact of relay 903, upper armature and back contact of relay 906 to the grounded conductor 7 5.). Relay 0-11 0 rates and immediately closes a lock ng circuit through its winding and locklng contact to the above traced ground. At this time, a circuit isalso com )letcd from battery, through the winding 0 relay 807, conductor 862,-lower intermediate front contact and armature of relay 911 to ground as above traced. Rela 8 07 operates and connects ground throng its inner armature and contact conductor 455 to operate tandem class relay 415 which serves as an indication to the sender that the existing call requires extension through a-tandem ollice as previously describe It will be observed that rela 807 functions similarly to the normal tan em trunk group relay 806 causing the operation of'relay 507. Consequently, the operation of relay 807 identifies the particular group of trunks outgoing from the switch 200 and leading to tandem office 260.

Should thecalled line be located in a distant ofiice other than ofiice 350, then, when a busy condition is encountered on all trunks lcadin to this oilice, a corres onding transfor r ay 912 will be operate in turn causmg the operation of a rela such as 819 w ich performs a function similar to relay 807. In this case, the operation of relay 810 will result in the identification and selection of a different group of tandem trunks which lead to a second tandem ofiice.

The operation of transfer relay 911 also completed a circuit from battery, through the winding of relay 805, right outer armature and contact of relay 802, conductor 863, lower outer armature and contact of relay 911, armature and back contact of relay 906 to the grounded conductor 753. Relay 805 at its right armature and contact opens the circuit of vertical magnet 214 which releases, in turn releasing rela 801. At the left outer armature and bac contact of relay 805, the holding circuit for the operated test relays 811, 812,

etc, is broken and these relays new release.

Relay 805 as described under normal tandem operation causes release relay 414 to loo operate with the consequent release of the pronnector 450, and the release of translator When transfer relay 911 operated, it c.\'- tended round through its lower inner armature and front contact, conductor 969 to hattery through the winding of relay 705. Re-

lay 705 in 0 crating removes ground from conductor 7 0 which causes the release of the ofilce trunk group relay 901. Relay 901 in turn causes the release of district trunk group relay 508. Relay 508 opens the lockmg circuit of relays 511 and 512 which release and in turn cause the release of trunk connector 550. The release of the olfice trunk group relay 901 also caused the release of the oflice class relay 406 in the sender. Belay 911 also brings about the release of ollicc frame and trunk connectors 650 and 655, together with the operated test relays 907, 908, etc., and trunk vertical magnet 311. Thus, the operation of transfer relay 911 as a result of all paths being busy at the ofii e switch resulted in the release of the district trunk connector, office trunk connector, ofiice frame connector, and the disconnection of the marker testing mechanism from the district and oflice switches. However, the marker is not released as yet since connector 450 is still operated, consequently vertical magnet 201 and frame connector 500 remain in their 0 erated condition.

When t e district trunk vertical magnet 214 released, it caused the release of relay 801 which in turn opened the locking cir cuit of slow relay 805 which began to release. A circuit is now completed to operate the particular district trunk connector associated with the newly selected group of tendem trunks which correspond to group relay 507. Accordingly, the trunk connector start relay 511 is operated from ground at the armature and back contact of relay 512, right hand winding of rela 511, right outer armature and contact of relay 507 to battery at the armature and contact of relay 509. Relay 511 looks in series with relay 512 which 0 crates. Thereupon, a circuit is complete for the actuation of multi-contact relay 5'13, and a circuit is also com leted for multi-contact relay 515, traceable rom battery through the winding of relay 515, right inner armature and contact of relay 507 to ground at the armature and contact of relay 512. With the relays 513 and 515 operated, the test conductors of the selected group of tandem trunks are connected to the testing mechanism 800. When relay 805 retracts its armatures as a result of the release of vertical magnet 214, a circuit is closed from battery through the winding of vertical magnet 216, conductor 259, contacts of connector 500, left armature and front cont-act of relay 507, conductor 557, right armature and contact of relay 805, conductor 854, to ground, through the contacts of relays 513 and 515. With the test conductors of the trunks 261, 262, etc., and the test conductors of links 264 and 265, etc, connected to the testing equipment 800, a test is made in the manner already described and the horizontal magnet corresponding to the first idle cross point is energized and the trunk 103 extended to the selected idle trunk.

Assuming link 266 and trunk 263 to be idle, then horizontal magnet 217 is operated and a circuit is completed from the grounded sleeve conductor of trunk 263, contacts of relays 515, 513 and 517, right armature and front contact of relay 809, left inner armature and backcontact of relay 802 to battery through the winding of relay 808. Relay 808 lmmediately closes a locking circuitthrough its winding and locking contact to the grounded conductor-.753. In a manner already described, relay 808 closes an operatmg circuit for relay 805. The operat on of relays 805 and 808 causes the o eration of sender releaserelay tn-which, as alreadydescribed, brings about the release of the sender connector 450 and the subs e quent release of the marker. The senderis not released at'this time, however, and since t had received a tandem class indication, it is now in readiness to transmit series of impulses by means of the impulse mechanism 420 over trunks 103 and 263 to the tandem oflice 260 where the selective switches are operated in such a manner as to select an idle trunk as 265 leading to the called office 350-. .For the manner in which the sender adjusts itself upon the rece tion of the class indication to transmit t ese impulses, and the manner in which the record may further be sent to the final oflice to cause the selection of the wanted line therein, reference may be had to the above mentioned pratent to S. B. Williams andE. S. Gibson,

0. 1,543,967, issued June 30, 1925.

While in the foregoing description, it has been chosen to illustrate the invention as applied to an all'trunks busy condition at the oflice switch 300, it is to be understood that the invention is not to be limited in this regard. The invention might equally well be applied to meet similar conditions existent at the district switch 200 or any other switch which is controlled in its selective operation by a marker controlling mechanlsm.

For details of operation referred to herein and not particularly illustrated referenceis made to the above mentioned patents to S. B. Wiliams, No. 1,517,331, December2, 1924 and SB. Williams and E. S. Gibson, No. 1,543,967, June 30, 1925, and W. W. (larpenter, Serial No. 703,362, filed April 1,1924.

TVhat is claimed is:

1. In a tele hone exchange system, calling lines, called was, selective switches for ex tending a calling line to one of said called lines, a mechanism accessible in common to a plurality of selective switches for control' ling the operation thereof, means in,said

ill

ill

mechanism for recording the designation of 

